Arrange sliced Italian bread flat on a baking sheet and cover with foil. Set aside until ready to use.
Preheat oven to 450 degrees F.
Combine sour cream, thyme, red pepper, cayenne pepper and four cheeses in a large bowl and blend thoroughly.
If serving family-style , spray an 8” x 10” casserole dish with pan spray, then use a spatula to transfer the mixture. For individual servings, spray eight individual heat-resistant serving bowls, such as soufflé cups, with pan spray and fill each with ½ cup of mixture. Place individual bowls on a baking sheet.
Using a large spoon, spread cheese mixture to create an even surface.
Place casserole dish or baking sheet with individual bowls on center rack in oven.
After five minutes, place baking sheet with bread, still covered, on top rack in oven. Bake for an additional five minutes.
Remove bread and fonduta from oven.
Garnish casserole dish with diced tomatoes and parsley in center of fonduta or divide evenly among smaller bowls.
Arrange bread slices around bowl(s) and serve immediately.